It is known practice to dye keratinous fibers, such as human hair, with dyeing compositions comprising oxidation dye precursors, generally known as oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidation bases are colorless or weakly colored compounds which, in combination with oxidizing products, can give rise, by an oxidative coupling process, to colored compounds.
It is also known that it is possible to vary the shades obtained with these oxidation bases by combining them with couplers or coloring modifiers, the latter being chosen, for example from aromatic meta-diamines, meta-aminophenols, meta-diphenols and certain heterocyclic compounds, such as indole compounds.
The variety of the molecules employed as oxidation bases and couplers makes it possible to obtain a rich palette of colors.
The “permanent” coloring obtained by these oxidation dyes furthermore should satisfy a certain number of requirements. The oxidation dyes should be toxicologically safe. It should also be possible to obtain shades within the desired intensity, and the oxidation dyes should behave well in the face of external agents, such as light, bad weather, washing, permanent waving, perspiration and rubbing.
The dyes should be able to cover white hair and be as non-selective as possible, i.e., make it possible to obtain the smallest possible differences in coloring along the same keratinous fiber, which is generally differentially sensitized (i.e., damaged) between its tip and its root.
It is already known to use aminopyrazolopyridine oxidation bases for the dyeing of keratinous fibers, for example, the aminopyrazolopyridine oxidation bases described in French Application Publication No. 2 801 308. These bases make it possible to obtain varied shades.
Furthermore, the use of dyeing compositions employing polyol solvents is known, for example, in French Application Publication No. 2 886 139.